Alterations in thyroid function tests are well documented in women taking estrogens. In addition, women with primary hypothyroidism have an increased need of exogenous thyroxine to maintain normal TSH and T4. This study is designed to determine if women with hypothyroidism who are taking thyroxine replacement require an adjustment to their dose when they begin to take estrogen, either as a contraceptive or postmenopausally. Used the CORE Lab.